/**
 *  Copyright (c) 1997-2013, www.tinygroup.org (luo_guo@icloud.com).
 *
 *  Licensed under the GPL, Version 3.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *       http://www.gnu.org/licenses/gpl.html
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.tinygroup.jspengine.compiler;

import java.util.*;
import javax.servlet.jsp.tagext.FunctionInfo;

import org.tinygroup.jspengine.JasperException;
import org.tinygroup.jspengine.runtime.ProtectedFunctionMapper;

/**
 * This class generates functions mappers for the EL expressions in the page.
 * Instead of a global mapper, a mapper is used for ecah call to EL evaluator,
 * thus avoiding the prefix overlapping and redefinition issues.
 * 
 * @author Kin-man Chung
 */

public class ELFunctionMapper {
	private int currFunc = 0;
	StringBuffer ds; // Contains codes to initialize the functions mappers.
	StringBuffer ss; // Contains declarations of the functions mappers.

	/**
	 * Creates the functions mappers for all EL expressions in the JSP page.
	 * 
	 * @param compiler
	 *            Current compiler, mainly for accessing error dispatcher.
	 * @param page
	 *            The current compilation unit.
	 */
	public static void map(Compiler compiler, Node.Nodes page)
			throws JasperException {

		ELFunctionMapper map = new ELFunctionMapper();
		map.ds = new StringBuffer();
		map.ss = new StringBuffer();

		page.visit(map.new ELFunctionVisitor());

		// Append the declarations to the root node
		String ds = map.ds.toString();
		if (ds.length() > 0) {
			Node root = page.getRoot();
			new Node.Declaration(map.ss.toString(), null, root);
			new Node.Declaration("static {\n" + ds + "}\n", null, root);
		}
	}

	/**
	 * A visitor for the page. The places where EL is allowed are scanned for
	 * functions, and if found functions mappers are created.
	 */
	class ELFunctionVisitor extends Node.Visitor {

		/**
		 * Use a global name map to facilitate reuse of function maps. The key
		 * used is prefix:function:uri.
		 */
		private HashMap gMap = new HashMap();

		public void visit(Node.ParamAction n) throws JasperException {
			doMap(n.getValue());
			visitBody(n);
		}

		public void visit(Node.IncludeAction n) throws JasperException {
			doMap(n.getPage());
			visitBody(n);
		}

		public void visit(Node.ForwardAction n) throws JasperException {
			doMap(n.getPage());
			visitBody(n);
		}

		public void visit(Node.SetProperty n) throws JasperException {
			doMap(n.getValue());
			visitBody(n);
		}

		public void visit(Node.UseBean n) throws JasperException {
			doMap(n.getBeanName());
			visitBody(n);
		}

		public void visit(Node.PlugIn n) throws JasperException {
			doMap(n.getHeight());
			doMap(n.getWidth());
			visitBody(n);
		}

		public void visit(Node.JspElement n) throws JasperException {

			Node.JspAttribute[] attrs = n.getJspAttributes();
			for (int i = 0; attrs != null && i < attrs.length; i++) {
				doMap(attrs[i]);
			}
			doMap(n.getNameAttribute());
			visitBody(n);
		}

		public void visit(Node.UninterpretedTag n) throws JasperException {

			Node.JspAttribute[] attrs = n.getJspAttributes();
			for (int i = 0; attrs != null && i < attrs.length; i++) {
				doMap(attrs[i]);
			}
			visitBody(n);
		}

		public void visit(Node.CustomTag n) throws JasperException {
			Node.JspAttribute[] attrs = n.getJspAttributes();
			for (int i = 0; attrs != null && i < attrs.length; i++) {
				doMap(attrs[i]);
			}
			visitBody(n);
		}

		public void visit(Node.ELExpression n) throws JasperException {
			doMap(n.getEL());
		}

		private void doMap(Node.JspAttribute attr) throws JasperException {
			if (attr != null) {
				doMap(attr.getEL());
			}
		}

		/**
		 * Creates function mappers, if needed, from ELNodes
		 */
		private void doMap(ELNode.Nodes el) throws JasperException {

			// Only care about functions in ELNode's
			class Fvisitor extends ELNode.Visitor {
				ArrayList funcs = new ArrayList();
				HashMap keyMap = new HashMap();

				public void visit(ELNode.Function n) throws JasperException {
					String key = n.getPrefix() + ":" + n.getName();
					if (!keyMap.containsKey(key)) {
						keyMap.put(key, "");
						funcs.add(n);
					}
				}
			}

			if (el == null) {
				return;
			}

			// First locate all unique functions in this EL
			Fvisitor fv = new Fvisitor();
			el.visit(fv);
			ArrayList functions = fv.funcs;

			if (functions.size() == 0) {
				return;
			}

			// Reuse a previous map if possible
			String decName = matchMap(functions);
			if (decName != null) {
				el.setMapName(decName);
				return;
			}

			// Generate declaration for the map statically
			decName = getMapName();
			ss.append("static private "
					+ ProtectedFunctionMapper.class.getName() + " " + decName
					+ ";\n");

			ds.append("  " + decName + "= ");
			ds.append(ProtectedFunctionMapper.class.getName());

			// Special case if there is only one function in the map
			String funcMethod = null;
			if (functions.size() == 1) {
				funcMethod = ".getMapForFunction";
			} else {
				ds.append(".getInstance();\n");
				funcMethod = "  " + decName + ".mapFunction";
			}

			// Setup arguments for either getMapForFunction or mapFunction
			for (int i = 0; i < functions.size(); i++) {
				ELNode.Function f = (ELNode.Function) functions.get(i);
				FunctionInfo funcInfo = f.getFunctionInfo();
				String key = f.getPrefix() + ":" + f.getName();
				ds.append(funcMethod + "(\"" + key + "\", "
						+ funcInfo.getFunctionClass() + ".class, " + '\"'
						+ f.getMethodName() + "\", " + "new Class[] {");
				String params[] = f.getParameters();
				for (int k = 0; k < params.length; k++) {
					if (k != 0) {
						ds.append(", ");
					}
					int iArray = params[k].indexOf('[');
					if (iArray < 0) {
						ds.append(params[k] + ".class");
					} else {
						String baseType = params[k].substring(0, iArray);
						ds.append("java.lang.reflect.Array.newInstance(");
						ds.append(baseType);
						ds.append(".class,");

						// Count the number of array dimension
						int aCount = 0;
						for (int jj = iArray; jj < params[k].length(); jj++) {
							if (params[k].charAt(jj) == '[') {
								aCount++;
							}
						}
						if (aCount == 1) {
							ds.append("0).getClass()");
						} else {
							ds.append("new int[" + aCount + "]).getClass()");
						}
					}
				}
				ds.append("});\n");
				// Put the current name in the global function map
				gMap.put(f.getPrefix() + ':' + f.getName() + ':' + f.getUri(),
						decName);
			}
			el.setMapName(decName);
		}

		/**
		 * Find the name of the function mapper for an EL. Reuse a previously
		 * generated one if possible.
		 * 
		 * @param functions
		 *            An ArrayList of ELNode.Function instances that represents
		 *            the functions in an EL
		 * @return A previous generated function mapper name that can be used by
		 *         this EL; null if none found.
		 */
		private String matchMap(ArrayList functions) {

			String mapName = null;
			for (int i = 0; i < functions.size(); i++) {
				ELNode.Function f = (ELNode.Function) functions.get(i);
				String temName = (String) gMap.get(f.getPrefix() + ':'
						+ f.getName() + ':' + f.getUri());
				if (temName == null) {
					return null;
				}
				if (mapName == null) {
					mapName = temName;
				} else if (!temName.equals(mapName)) {
					// If not all in the previous match, then no match.
					return null;
				}
			}
			return mapName;
		}

		/*
		 * @return An unique name for a function mapper.
		 */
		private String getMapName() {
			return "_jspx_fnmap_" + currFunc++;
		}
	}
}
